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Yr 3 Sem 1 > Week 3 > Flashcards

Week 3 Flashcards

1
Q

What is the digestive system composed of?

A

Gastrointestinal tract

Accessory digestive organs

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2
Q

Where is the liver located?

A

RUQ & part of LUQ

All of Rt hypochondrium, most of epigastrium, some of Lt hypochondrium

Separated from thoracic cavity by the diaphragm

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3
Q

Explain the surfaces of the liver

A

Diaphragmatic surface
Smooth, dome shaped, convex

Related to the concave, inf. aspect of the diaphragm

Covered with peritoneum except posteriorly where the bare area of the liver lies in contact with diaphragm

Visceral surface of the liver
Inferior & posterior aspect

Is covered with peritoneum except near the gall bladder and the porta hepatis

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4
Q

What is the porta hepatis?

A

Transverse fissure on the visceral surface of the liver between the caudate & quadrate lobes

Gives passage to the:

Portal vein

Hepatic artery

Hepatic nerve plexus

Hepatic ducts

Lymphatic vessels

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5
Q

What is the lesser omentum?

A

Double fold of peritoneum which connects the lesser curvature of the stomach & the proximal duodenum to the liver

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6
Q

What are the two ligaments of the lesser omentum?

A

Hepatoduodenal ligament: a thickened region on the free edge

Encloses the portal triad (bile duct, hepatic a., portal v.) along with lymph nodes, lymphatic vessels and the hepatic plexus of nerves

Hepatogastric ligament: the remaining, sheet-like aspect of the lesser omentum

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7
Q

Describe the peritoneal ligaments of the liver

A

Falciform ligament
Connects liver to anterior abdominal wall & diaphragm

Round ligament (Ligament teres)	
Contained within the free edge of the falciform ligament

Fibrous remnant of the umbilical vein (carried well-oxygenated, nutrient-rich blood from placenta to foetus)

Ligamentum Venosum
Fibrous remnant of the ductus venosus
In the foetus, connects the left umbilical vein to the IVC (allows blood to bypass the liver)

The above 3 ligaments divide the liver into Rt and Lt lobes

Coronary ligament
Peritoneal reflection from the liver to the diaphragm

Demarcates the bare area of the liver

Triangular ligaments
Peritoneal folds that connect the liver to the diaphragm

Rt triangular ligament: situated at the Rt extremity of the bare area

Lt triangular ligament: continuous with falciform ligament anteriorly

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8
Q

What is the arterial supply to the liver?

A 
Portal Vein (70%)
Formed by SMV & splenic v. just post. to the neck of pancreas

Conveys nutrient-rich blood from stomach and intestines

Hepatic Artery (30%) 
Branch of Celiac a. – provides oxygenated blood

At or close to porta hepatis, both vessels divide into Lt + Rt branches (supply corresponding part of liver)

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9
Q

What is the venous supply to the liver?

A

Hepatic veins (open into the IVC just inf. to diaphragm)

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10
Q

What is the lymphatic drainage of the liver?

A

Superficial lymphatics drain to hepatic & phrenic nodes

  • Hepatic nodes  celiac nodes  cisterna chyli (dilated sac at inf. end of thoracic duct)
  • Phrenic nodes  posterior mediastinal nodes  thoracic duct or Rt lymphatic duct

Deep lymphatics drain to hepatic nodes

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11
Q

What is the nerve supply of the liver?

A 
Hepatic plexus consisting of:
Sympathetic fibres (T5-9 via celiac plexus) & parasympathetic fibres (CNX Vagus)
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12
Q

What is the role of the liver?

A

Synthesis
Bile (~1L daily)
Plasma proteins e.g. clotting factors, albumin
Hormones e.g. angiotensinogen, erythropoietin
Haemopoiesis (foetal development)

Detoxification
Drugs, alcohol
Conversion of ammonia to urea

Metabolism & storage
Fat, carbohydrates, amino acids, vitamins & minerals (iron, vitamins A, B12 & D)

Excretion
Bilirubin in bile (erythrocyte breakdown)

Immune function
Phagocytic activity (Kupffer cells)
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13
Q

What is the functional unit of the liver?

A

Liver lobules

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14
Q

What is the direction of flow from lobules (histology)?

A

Blood flows from portal tract to the central vein (via sinusoids)

Bile flows from central areas to portal tracts (via bile canaliculi)

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15
Q

What is an acinus?

A

a kernel-shaped area of liver parenchyma that is centred upon a portal tract
Divided into three zones:
Zone 1 is closest to the portal tract (receives the most O2)

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16
Q

What is the structure of the biliary tree?

A

Blood passing into central v. eventually enters hepatic vv  IVC

Bile entering the bile ducts eventually enters the Lt and Rt hepatic ducts, which drain the Lt and Rt lobes of the liver, respectively. These unite to form the common hepatic duct

Common hepatic duct merges with the cystic duct of the gall bladder to form the bile duct (formerly called the common bile duct)

Hepatopancreatic ampulla is formed by union of bile duct & major pancreatic duct

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17
Q

What is the gallbladder?

A

Pear-shaped muscular sac

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18
Q

What is the function of the gallbladder?

A

Storage & concentration of bile (capacity ~50 ml)

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19
Q

What are the parts of the gallbladder?

A

Fundus: wide end, projects from the inferior border of the liver

Body: contacts the visceral surface of the liver

Neck: narrow tapered region, makes an S-shaped bend and is continuous with the cystic duct

20
Q

What is the arterial supply of the gallbladder?

A

Cystic a. (off Rt hepatic a.)

21
Q

What is the Venous drainage of the gallbladder?

A

Cystic vv directly into liver or into portal vein

22
Q

What is the lymphatic drainage of the gall bladder?

A

Cystic nodes ->Hepatic nodes ->Celiac nodes

23
Q

What is the nerve supply of the gallbladder?

A

Parasympathetic: CNX Vagus

Sympathetic: Splanchnic nn T5-9 (via celiac plexus)

Sensory: Rt Phrenic n.

24
Q

Explain the histology of the gallbladder

A

Mucosa:
Simple columnar epithelium that possess microvilli (absorption)
When empty the mucosa is thrown into honeycomb-like folds

Note: the GB wall lacks a muscularis mucosae and submucosa

Muscularis:
Contains smooth m., collagen & elastin
Contracts in response to cholecystokinin & vagal stimulation

Adventitia/Serosa:
Surface attached to liver has an adventitia
Peritoneal surface - serosa

25
Describe the pancreas
Elongated tadpole-shaped gland, ~ 15cm long Found in the epigastric & Lt hypochondriac regions Stretches transversely behind stomach, in between spleen & duodenum Retroperitoneal Does not have a distinct fibrous capsule, instead has a very thin capsule that invaginates into gland (forms septae)
26
What is the function of the pancreas?
Functions as both an exocrine (chemicals) & endocrine gland (hormones)
27
What are the regions of the pancreas?
Head of the pancreas Expanded part of the gland found within the duodenum Firmly attached to medial aspect of D2 & D3 Bile duct situated in a groove posterior/superior to the head or sometimes within the parenchyme itself Uncinate process: lower part of the head that projects upwards to the left (L. ‘hook’) Neck of the pancreas Short region (1.5 - 2cm) between the head and body Anteriorly: groove for the gastroduodenal a. Posteriorly: union of the SMV and Splenic vein (forming the Portal vein) Body of the pancreas Crosses the aorta (level of L2) Anteriorly: covered with peritoneum Posteriorly: aorta & origin of SMA; Lt adrenal gland, Lt kidney & renal vessels, left crus of the diaphragm, splenic vein Tail of the pancreas Anterior to the Lt kidney Closely related to the hilum of the spleen & Lt colic flexure Passes between layers of the splenorenal ligament (peritoneal ligament)
28
What are the pancreatic ducts?
MAIN PANCREATIC DUCT Begins in the tail of the pancreas and runs to the head Found more in the posterior aspect of the pancreas Unites with bile duct to form the hepatopancreatic ampulla (opens into D2: major duodenal papilla) ACCESSORY PANCREATIC DUCT Drains the inferior part of the head Opens into the duodenum (minor duodenal papilla) In 60% of people, it communicates with the main pancreatic duct
29
What are the sphincters of the pancreas?
Smooth m. sphincters control the flow of bile & pancreatic juice Sphincter of the pancreatic duct around the terminal part of the pancreatic duct Sphincter of the bile duct around terminal part of the bile duct ``` Hepatopancreatic sphincter (sphincter of Oddi) around the hepatopancreatic ampulla ``` Sphincters are closed when no digestion is occurring (bile secreted by liver gets stored in GB)
30
What is the arterial supply to the pancreas?
Mainly from branches (~10) of the splenic artery Anterior & posterior superior pancreaticoduodenal aa (from gastroduodenal a) Anterior & posterior inferior pancreaticoduodenal aa (from SMA)
31
What is the venous drainage of the pancreas?
Pancreatic veins (most are tributaries of the splenic vein, some the SMV)
32
What is the lymphatic drainage of the pancreas?
Mostly the pancreaticosplenic nodes Efferents from these drain into the celiac, hepatic & superior mesenteric nodes
33
What is the nerve supply of the pancreas?
Parasympathetic: CNX Vagus Sympathetic: abdominopelvic splanchnic nerves (T5-9) via the celiac ganglion
34
Describe the histology of the pancreas
EXOCRINE PORTION Acinar cells – form the bulk of the pancreas Acinar cells possess abundant rough ER and zymogen granules (inactive enzymes) Secrete enzyme-rich pancreatic juice into the ductal system Ductal cells also secrete water & HCO3- ENDOCRINE PORTION Pancreatic islets are scattered among the acinar cells Contain hormone-producing cells (endocrine function)
35
What is digestion?
catabolic process that breaks down complex food molecules to monomers
36
What is absorption?
passage of digested end products from the lumen of the GIT through mucosal cells into the blood or lymph
37
What do digestion and absorption rely on?
bile and pancreatic secretions
38
What are the components of bile?
Bile salts* Phospholipids (lecithin)* Bile pigments (bilirubin) Cholesterol, triglycerides Electrolytes *Only bile salts and phospholipids assist in digestion & absorption 95% of bile salts are recycled by the enterohepatic circulation: reabsorbed in the ileum, returned to the liver (portal vein) & resecreted in newly formed bile
39
What are the functions of bile?
DIGESTION & ABSORPTION Emulsification of large fat particles into small droplets (bile salts have detergent properties) This increases SA available for lipases to act upon the fat molecules Bile salts & phospholipids interact with the breakdown products of fat digestion – forming micelles Micelles “ferry” free fatty acids & monoglycerides to the intestinal mucosa for absorption EXCRETION OF WASTE PRODUCTS Bilirubin & excess cholesterol Pathologies that interfere with bilirubin excretion can result in jaundice
40
What are the key contents of pancreatic juice?
enzymes, water & electrolytes (HCO3-)
41
What are the pancreatic enzymes?
Proteases: digest proteins Amylase: digests starch Lipases: digest emulsified fats Nucleases: digest nucleic acids
42
What is enteropeptidase?
(brush border enzyme) - converts pancreatic proteases to their active form Trypsinogen -->trypsin Chymotrypsinogen -->chymotrypsin
43
Describe the regulation of bile and pancreatic secretion
HORMONAL REGULATION CCK & secretin released by duodenal enteroendocrine cells, in response to fatty, acidic or protein-rich chyme CCK: pancreatic secretion (enzyme component), GB contraction & relaxation of hepatopancreatic sphincter Secretin: pancreatic secretion (H2O & HCO3- component), bile secretion Return of bile salts from enterohepatic circulation: bile secretion NERVOUS REGULATION Vagal stimulation: pancreatic secretion & GB contraction
44
Describe the chemistry of digestion
Digestion involves hydrolysis: water is added to each molecular bond that is broken DIGESTIVE ENZYMES Are produced by various organs of the GIT Act as organic catalysts (accelerate chemical reactions without appearing in final product) Each enzyme possesses an active site for a specific substrate Function optimally at a specific pH Most are synthesised as zymogens (proenzymes)
45
What are absorption methods?
Small intestine receives ~9L of water daily and absorbs ~95% via osmosis (remaining fluid absorbed in large intestine) Glucose & amino acids Enter epithelial cells through cotransport with Na+ Enter blood via facilitated diffusion Fatty acids & monoglycerides Diffuse from micelles into epithelial cells Are repackaged with other lipids & proteins into chylomicrons Chylomicrons exit epithelial cells via exocytosis and enter lacteals Vitamins Fat-soluble vitamins (A, D, E & K) also rely on micelles for ‘ferrying’ to epithelial cells (these enter via diffusion) Vitamin B12 needs to be bound to intrinsic factor The B12-IF complex triggers endocytosis
46
What is an example of a food component that cannot be digested and is excreted in faeces?
Cellulose

Yr 3 Sem 1 (7 decks)

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